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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Harini Katakam <harini.katakam@xilinx.com>,
        Michal Simek <michal.simek@xilinx.com>,
        Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>,
        Claudiu Beznea <claudiu.beznea@microchip.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 071/132] net: macb: Increment rx bd head after allocating skb and buffer
Date:   Mon, 23 May 2022 19:04:40 +0200
Message-Id: <20220523165834.928906858@linuxfoundation.org>
In-Reply-To: <20220523165823.492309987@linuxfoundation.org>
References: <20220523165823.492309987@linuxfoundation.org>
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From: Harini Katakam <harini.katakam@xilinx.com>

[ Upstream commit 9500acc631dbb8b73166e25700e656b11f6007b6 ]

In gem_rx_refill rx_prepared_head is incremented at the beginning of
the while loop preparing the skb and data buffers. If the skb or data
buffer allocation fails, this BD will be unusable BDs until the head
loops back to the same BD (and obviously buffer allocation succeeds).
In the unlikely event that there's a string of allocation failures,
there will be an equal number of unusable BDs and an inconsistent RX
BD chain. Hence increment the head at the end of the while loop to be
clean.

Fixes: 4df95131ea80 ("net/macb: change RX path for GEM")
Signed-off-by: Harini Katakam <harini.katakam@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220512171900.32593-1-harini.katakam@xilinx.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/cadence/macb_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 217c1a0f8940..2fd3dd4b8b81 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -1250,7 +1250,6 @@ static void gem_rx_refill(struct macb_queue *queue)
 		/* Make hw descriptor updates visible to CPU */
 		rmb();
 
-		queue->rx_prepared_head++;
 		desc = macb_rx_desc(queue, entry);
 
 		if (!queue->rx_skbuff[entry]) {
@@ -1289,6 +1288,7 @@ static void gem_rx_refill(struct macb_queue *queue)
 			dma_wmb();
 			desc->addr &= ~MACB_BIT(RX_USED);
 		}
+		queue->rx_prepared_head++;
 	}
 
 	/* Make descriptor updates visible to hardware */
-- 
2.35.1